Water Quality Data Assessment
What is water quality assessment?
The assessment of water quality in North Carolina is required under Sections 303(d) and 305(b) of the Clean Water Act and is to be reported on every two years. This assessment is formally known as the Integrated Report. The assessment is conducted in 3 parts:
- The first part of the assessment is collecting water quality data; DWR and Monitoring Coalitions collect thousands of surface water quality samples throughout NC’s lakes, rivers, and streams for a variety of parameters.
- The second part of the assessment is comparing each water quality sample collected to the appropriate North Carolina water quality standard. If enough water quality samples exceed the respective water quality standard for that parameter then the waterbody could be considered impaired depending on the assessment methodology.
- The third part of the assessment is the assessment methodology. The assessment methodology describes how many exceedances of water quality standards a waterbody can have for a particular pollutant, the data window used for the assessment (usually 5 years), and what integrated reporting category will be assigned to each waterbody-parameter combination.
Each monitored waterbody in North Carolina receives an assessment every two years. The most current assessment is the Draft 2014 Integrated Report and is available on the right side of the page. The first page of the document defines the assessment categories. Additional assessment categories are typically added from year to year to aid in tracking assessment history and restoration activities.
What are impaired waters?
Impaired waters are a subset of the assessments made where water quality samples for a particular parameter on a waterbody exceed water quality standards and the assessment methodology has determined that the waterbody is indeed impaired for the particular parameter. Impaired waters are grouped into two categories:
- Category 4 assessments are those that do not need a TMDL.
- Category 5 assessments are those that do need a TMDL (303(d) List).
What is the 303(d) List?
The 303(d) list is simply the Category 5 impaired waters that need a TMDL as shown above. These waters are assembled in a single document and sent to EPA on April 1st of every even numberd year, per 40 CFR 130.7. EPA must approve, disapprove, or partially approve each 303(d) list.
How are water quality standards made and do they change?
To learn about all about water quality standards please visit the water quality standards page.
How is the assessment methodology made and does it change?
The assessment methodology, which includes 303(d) listing methods, is set to be consistent with North Carolina water quality standards and EPA guidance and generally does not change from year to year, unless standards or guidance changes. However, substantial changes to the methodology were made in 2014. The methodology for the 2014 303(d) list was the first such methodology approved by the North Carolina Environmental Management Commission.
Who collects the data?
Data used for water quality assessment is primarily collected by DWR's Ambient Monitoring System, NPDES Discharge Monitoring Coalitions , and Biological Assessment Branch, the NC DHHS Division of Public Health, and the United States Geological Survey. Local governments and environmental groups as well as industry, municipal and university coalitions also provide data. Submitted data sets must include an approved Quality Assurance Project Plan (QAPP) to assure that the data were collected in a manner consistent with agency data. A standing solicitation for data is listed below.
Where to find data
DWR stores data from the Ambient Monitoring System on EPA's STORET online database. Guidance on how to search and download data is available on the DWR AMS homepage.
How you can submit data
DWR invites all interested parties to submit water quality data and information. The quality and reliability of data submitted determines the programs and projects for which the data can be used. DWR uses only the highest quality data for regulatory decision-making and water quality assessment.IF YOU INTEND TO SUBMIT DATA FOR DWR USE, PLEASE CONTACT US BEFORE BEGINNING DATA AND INFORMATION COLLECTION, TO ENSURE THAT WHAT YOU SUBMIT IS USABLE FOR ITS INTENDED PURPOSE.
|Submitting Data for Non-Regulatory Use ||Submitting Data for Regulatory Use |
- Water quality data not from a certified lab
- Water quality data for which NC has no standard
Data must meet all of the following criteria:
- From representative location
- Sufficient number of samples
- From certified lab
- Applicable NC standard
- Documented QA/QC
- Support for water quality data
- Further investigation
- 303(d) listing
- Use support
- Standards attainment
- Water quality modeling
What pollution sources are causing the impairment?
DWR Basinwide Planning Reports are an excellent resource for finding detailed information on the probable sources of pollution for 303(d) listed waterbodies.
How are waters removed from the 303(d )list?
Waters are removed when either a TMDL, or TMDL Alternative, is completed or when monitoring data shows that the waterbody is in compliance with water quality standards. Waters that are suspected to be impaired due to natural conditions may be removed with approval from the US EPA with appropriate documentation.
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